1. Field of the Invention
The present invention relates to a method of preparing microcapsules and, more specifically, to a method of preparing toners of a multilayered structure.
2. Description of the Related Art
In numerous technical fields, attention is now being paid to using microcapsules as functional particles.
For instance, imaging toners are required to serve high-performance functions. Thus various techniques for producing microcapsules of a multilayered structure have been proposed to this end, including, e.g. methods for producing microcapsule toners by polymerization with a view to fixing them with low energy (U.S. Pat. No. 3,080,250, Japanese Patent Publication No. 31066/1984 and Japanese Patent Publication No. 36934/1989); a method for producing toners having electrification-controlling resin films around them using a dry high speed impact technique with electrification control in mind (Japanese Patent Laid-Open Publication No. 62666/1988); and a method for producing toners by treating their surfaces with finely divided resin powders for the purpose of imparting blocking resistance to them (Japanese Patent Laid-Open Publication No. 105261/1989).
Problems with the toners obtained by fixing coats to them with the aid of a high speed impinge or impact force (Japanese Patent Laid-Open Publication Nos. 62666/1988 and 105261/1989), however, are that the coats are so much less adhesive to the toner surfaces and undergo such large variations in thickness or adhesion that they degrade during use, separating off the toner surfaces or undergoing changes in their surface shapes, etc., thus resulting in a drop of the quality of the resulting images. The microcapsule-coating methods (Japanese Patent Nos. 310666/1984 and 61141/1987) also involve similar problems or offer difficulties in connection with toners' durability and coagulation stability due to the coats being thin and varying largely in thickness or for other reasons.
In most of the conventional methods, the toners' cores and coats must stand up to the heat or pressure which are used to deposit and fix the coats to the toners' cores. For that reason, there is another problem that some limitation is placed on the materials of which the toners' cores and coats are made.
Generally speaking, it is thus desired to develop a method for producing microcapsules well adapted for various technical fields, in which various coats can be formed on various cores at any desired but uniformly controlled coat thickness.